1. Field of the Invention
The present invention relates to an apparatus and a method of displaying a car-navigating map.
2. Description of the Related Art
In making a car-navigating map of an area including a city, level of detailedness of the map is usually determined by the population of the city. For example, levels of detailedness of car-navigating maps for predetermined areas are classified so that a somewhat detailed car-navigating map is prepared for an area including a city of a population of 200,000 or more and a more detailed car-navigating map is prepared for an area including a city for which The Japanese Geographical Survey Institute issued a map of a scale of 1/10,000.
When a car-navigating map displaying system, for example, establishes the three levels of level A, level B and level C of detailedness and a motorcar goes to an area of level B through an area of level A or to an area of a lower level, for example, from the area of level B to the area of level C lower than level B, there is a problem that a representation of the same road to be traveled by the motorcar may be discontinued between the areas of the different levels.
This problem will be described with reference to FIGS. 8 and 9 hereinafter. As shown in FIGS. 8 and 9, it is assumed that the system displays all of roads b and c at level B and continues to display the roads b at level B but displays none of the roads at level C. When a automotive vehicle or motorcar X now travels along a road c1 toward north and a current position of the motorcar X is in the area of level B as shown in FIG. 8, the system displays the road c1. However, the system discontinues displaying the road c1 in the area of level C as the motorcar X approaches a boundary between the areas of levels B and C as shown in FIG. 9. Thus, such discontinuity in displaying a road due to a difference between levels of detailedness may mislead a driver of the motorcar X to judge that a traveled road reaches an end.